ReviewHip dislocations—Epidemiology, treatment, and outcomes
Introduction
Traumatic dislocations of the hip appear to be on the rise in North America. They can be divided into simple and complex dislocations. Simple dislocations do not have an associated fracture and may be less common than previously thought.19, 23 Complex dislocations have associated fractures.Various fracture classification systems are used for hip dislocation. The Thomas–Epstein classification of posterior hip dislocations includes associated fractures for Types II–V.12 The Pipkin classification system is used for posterior hip dislocations associated with femoral head fractures.12 The Levin classification can be used for both anterior fracture-dislocations and posterior fracture-dislocations.12 The treatment of complex hip dislocations (fracture-dislocations) is generally predicated on specific treatments of the associated fracture (e.g., femoral head fracture, femoral neck fracture, acetabular fracture, etc.). However, fracture-dislocations of the hip (complex fracture-dislocations) are not the focus of this paper. This review will focus on the treatment of simple dislocations of the hip.
Multidetector CT, hip arthroscopy, and high field MRI has further defined the pathoanatomy of hip dislocations. In addition, increasing detection of femoroacetabular impingement may ultimately establish a role for hip dislocation in the pathogenesis of femoroacetabular impingement. We will review the mechanism of injury, epidemiology, associated injuries, evaluation, treatment, and functional outcomes of simple hip dislocations.
Section snippets
Mechanism of injury
The depth of the acetabulum and labrum, the thick joint capsule, and the strong muscular support structures, make this a true ball and socket joint unlikely to dislocate.1, 34 Arvidsson demonstrated that a traction force of 400 N (90 lbs) was needed in order to cause separation of the hip joint.2 The direction of the force vector applied and the position of the lower limb at the time of injury determined the direction and type of the dislocation.1
Anterior hip dislocations represent 10% of all
Epidemiology
Epstein reported that the majority of hip dislocations occurred in males 16–40 years old as a result of motor vehicle accidents.9 Other investigators have reported that 70–100% of posterior hip dislocations result from motor vehicle collisions.7, 14, 29, 34 Nevertheless, Pape et al. reviewed 31 total traumatic hip dislocations and found only 12 were the result of motorcycle accidents.25 Unrestrained occupants are at significantly higher risk for hip dislocation than those wearing restraints.34
Associated injuries
There is a 95% incidence of injury to other areas of the body in patients with hip dislocations.13 Acetabular fractures were seen in 70% of patients with traumatic hip dislocations, other lower extremity fractures in 23%, upper extremity fractures in 21%, closed head injuries in 24%, thoracic injuries in 21%, and abdominal injuries in 15%.13 Over two-thirds of patients sustained a serious non-orthopaedic injury. These authors recommended that patients with a hip dislocation after a motor
Evaluation
Advanced traumatic life support (ATLS) is the most important part of the initial assessment of the patient with a hip dislocation. After ATLS has been initiated, physical examination will often reveal the direction of the hip dislocation. The classic appearance of posterior hip dislocation is a leg that is flexed, internally rotated, adducted, and foreshortened. In contrast, patients with anterior dislocations will hold their leg in external rotation, extension, and abduction.4 Patients may
Treatment
Attempted closed reduction of a dislocation within 6 h of the injury is preferred in order to decrease the likelihood of avascular necrosis of the femoral head.17 Thompson and Epstein reported that multiple attempts at closed reduction resulted in poorer long-term results.33 At our institution, closed reduction is performed as soon as safely possible in the trauma bay with the patient under conscious sedation.
It is not necessary to become proficient with all hip reduction techniques, but mastery
Functional outcome and prognosis
Epstein previously reported fair/poor results in one-third of patients with hip dislocations.9 Outcomes following simple hip dislocation span the gamut from an essentially normal hip to a severely painful, arthritic hip joint.13, 34 Factors which influence the outcome include the extent of other severe injuries, the time to reduction, the direction of the dislocation, and the overall condition of the patient prior to dislocation. The outcome for individual patients depends largely on the
Conclusion
The frequency of hip dislocations appears to be on the rise in North America. Hip dislocations usually result from motor vehicle accidents and are much more common in men. Heightened vigilance for associated injuries such as those to the ipsilateral knee with a low threshold for the use of knee MRI is recommended. Multidetector CT has improved our ability to detect intraarticular loose bodies and occult fractures. Expanded use of high field MRI and hip arthroscopy has improved our ability to
Conflict of interest
The authors state that there is no conflict of interest.
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